Range finder



May 23, 1939. D. P. BENNETT RANGE FINDER Fi led Sept. 17, 1938 II ll WIUHHLMMMMM ////////////////////d INVENTOR DONALD P. BENNETT ATTORNEYS Patented May 23, 1939 UNITED STATES PATENT OFFICE 8 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed, if patented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me of any royalty there This invention relates to range finding and it is more particularly concerned with a device for determining the location of distant objects by using circular photographs such as those described in my co-pending application, Serial No. 230,368, filed September 17, 1938.

One of the objects of this invention is the provision of a device of the type mentioned which is simple and inexpensive to manufacture and operate and which provides a more rapid and more accurate method of determining locations of distant objects such as is required in fire detection work.

The following description considered together with the accompanying drawing will disclose this invention more fully, its construction, arrangements, combinations, and operations .of parts and other objects and advantages thereof will be apparent.

In the drawing:

Figure 1 is a plan view of an illustrative embodiment of this invention.

parts shown in section along the line 2-2.

pointer assembly taken along the line 33 of Figure 2.

line 4-4 of Figure 2.

Referring with more particularity to the draw- 1 a vertical base support 6. At the center of'said table 5 a vertical column I rotatably supports an alidade, which alidade consists of a horizon-;

Figure 2 is a side view of Figure-1 with some Figure 4 is an enlarged fragmentary view of a section of the plane table broken away along thev a stub shaft l6 of the rider l3. Through said stub shaft a set screw H is disposed for the purposeof securing the rider 13 in desired positions along the beam I 2.

. An-annularly'recessed clamping ring l8 is removably disposed on and is concentric with the' plane table 5 by means of screws IS. The clamping ring I8 is adapted to secure a circular photograph 20 of the type hereinabove mentioned, superimposed by a transparent plate 2|, such as celluloid, glass, isinglass, and so forth, substantially as shown in Figure 4.

r The operation of this invention is as follows: The photograph 20 together with the transparent plate 2| superimposed thereupon is fixed on the plane table 5 by means of the clamping ring la, the photograph being a perspective reproduction of the field of view surrounding the instrument and is of the type'described in my above-referred to co-pending application for patent. Such photograph need not necessarily be one which was taken with a camera set at the exact center of the plane table 5, but in extreme cases the camera may be as much as 20 or 30 feet therefrom without materially affecting the accuracy of the results. Thephotograph is concentrically mounted on the plane table and it is orientated in a position such that the images of the objects on the photograph coincide radiallywith the objects themselves. To determine the location of a selected object, the object is sighted along the beam l2 by rotating the alidade assembly. This establishes the bearing of the object. All objects seen along this bearing'will be in reproduction directly beneath the bearing line on the photograph. It is now only necessary to determine the location of the selected object along that bearing. This is accomplished by moving the rider l3 together with the spattered mirror l4 along the beam l2 until both the image of the real object and the reflected image of the same object reproduced on the photograph coincide in the observers eye by superimposition. When this is established, the pointer IS in a vertical position indicates the. object on the photograph. With the object definitely located on the photograph its distance from the point of observation or any other point may be determined by several methods. For example, it may be accomplished by direct measurement on the photograph. Also the photograph 20 or the transparent plate 2| may be previously prepared with designations of known landmarks, place names and other data for identification and the location of objects under observation defined with respect thereto.

This device has a wide range of uses. For example, in forestry work, it is useful in locating forest fires; It'is especiallydesirable for untrained lookouts or those unfamiliar with the natural landmarks of a particular area, furnishing elevations and facsimile representations of landmarks.

Ordinarily, maps are used instead of photographs in similar devices and the lookout upon discovering a fire transmits the bearing and the approximate location by telephone to a dispatching ofiicer. The use of the photograph in place of the map facilitates the identification of landmarks near the fire which might not ordinarily appear on a map. The dispatching ofllcer, if equipped with a duplicate set of photographs representing each lookout tower of his fire control district, would be able to obtain the same viewpoint as each lookout. This facilitates the quickest determination of the exact location of the fire.

Having thus described my invention, I claim:

1. A range finding device comprising a table having thereon a circular perspective reproduc-- tion of the surrounding field of view, an alidade rotatably mounted on said table, a horizontal beam mounted on said alidade, a rider slidably mounted on said beam and a spattered silvered mirror fixed to said rider.

2. A device for locating distant objects comprising a table, an alidade rotatably mounted on said table having thereon a circular perspective reproduction of the surrounding field of view, a horizontal beam on said alidade, a spattered silvered mirror fixed to said rider, and means for securing said perspective reproduction on said table.

3. A device for determining locations of distant objects comprising a table, an alidade rotatably mounted on said table, a horizontal beam mounted on said alidade, a rider slidably mounted on said beam, a spattered silvered mirror fixed to said rider, indicating means depending from said rider over said table,and a circular perspective reproduction of the surrounding field of view with means for securing it on said table.

4. A device for locating distant objects comprising a circular table secured to a base support, means for securing a circular photograph on said table, an alidade rotatably mounted on said table, said alidade having two uprights at its opposite ends, a horizontal beam disposed across said uprights, a rider slidably mounted on said beam,

a spattered silvered mirror fixed to said rider, and a pointer suspended from said rider.

' 5. A device for locating distant objects comprising a table, an alidade rotatably mounted on said table, a horizontal beam mounted on said alidade, a rider slidably mounted on said beam, a spattered silvered mirror fixed to said rider, indicating means depending from said rider over said table, means for clamping said rider to said beam, and a circular photographic perspective reproduction of the surrounding field of view with means for securing it on said table beneath said pointer. 4

6. A device of the character described comprising a horizontal table, an alidade pivoted to the center of said table, a horizontal beam mounted on said alidade, a sleeve member slidably mounted on said beam, a spattered silvered mirror fixed to said sleeve member, a pointer hingedly mounted on said sleeve member, a set, screw disposed on said sleeve member for clamping it to said beam and a circular photograph with means for removably securing it on said tablebeneath said pointer.

7. A device for locating distant objects comprising a circular table, an alidade concentrically pivoted on said table, a horizontal beam mounted on said alidade, a rider slidably mounted on said beam, a spattered silvered reflector fixed to said rider at an angle of substantially 45 with the horizontal, a pointer hingedly mounted on a stub shaft of said rider, means for clamping said rider to said beam, and a circular photographic perspective reproduction of the surrounding field of view with means for concentrically securing it on said table beneath said pointer.

8. An article of manufacture comprising a circular table adapted to be disposed on a vertical support; an alidade concentrically mounted on said table, said alidade comprising a horizontal beam and two diametrically opposite uprights; a horizontal rod member secured to said alidade near the upper ends of said uprights; a rider slidably mounted on said rod; a spattered silvered reflector fixed to said rider at an angle of 45 with said horizontal beam; a pointer hingedly mounted on a stub shaft of said rider and depending therefrom over said table; means for clamping said rider to said beam; and a clamping ring concentric with the table for removably clamping on said table beneath said pointer a circular photographic perspective reproduction of the surrounding field of view with the images of the objects oriented in a position to coincide radially with the objects themselves.

DONALD P. BENNE'I'I'. 

